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Technical Briefs

Development of a Real-Time NOx Prediction Model Based on Heat Release Analysis in a Direct-Injection Diesel Engine

[+] Author and Article Information
Chao Zhang

e-mail:: zhangc@engga.uwo.ca
Department of Mechanical and Materials Engineering,
The University of Western Ontario,
London, ON N6A 5B9, Canada

1Correspondence author.

Contributed by the Combustion and Fuels Committee of ASME for publication in the JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER. Manuscript received February 10, 2013; final manuscript received October 8, 2013; published online November 14, 2013. Assoc. Editor: Kalyan Annamalai.

J. Eng. Gas Turbines Power 136(3), 034501 (Nov 14, 2013) (4 pages) Paper No: GTP-13-1049; doi: 10.1115/1.4025789 History: Received February 10, 2013; Revised October 08, 2013

A prediction model, which describes linear relationship between the nitrogen oxides (NOx) emissions and the in-cylinder heat release rate in a direct-injection diesel engine, was developed through numerical simulations. A modified KIVA-3 V code was used to calculate NOx formations and to conduct heat release analyses in a direct-injection diesel engine under different operating conditions. The numerical simulation results indicated that the NOx formation amount was related to both the magnitude and the timing of the peak heat release rate in each engine cycle. Based on the above observations, a control-oriented dynamic NOx model was constructed and then implemented into a feedback emission control system on a small diesel engine. A new parameter—combustion acceleration—was proposed in this research to describe the intensity of the premixed combustion. Experimental work was also conducted to measure the real-time in-cylinder pressure at each crank-angle when the engine was running and the heat release rate was calculated instantaneously to control an exhaust gas recirculation (EGR) valve. The experimental results showed that the proposed NOx prediction model was effective in controlling NOx emissions under high rpm conditions.

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Figures

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Fig. 1

Comparisons of measured and predicted in-cylinder pressure and heat release rate: (a) low load condition and (b) high load condition

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Fig. 2

Comparisons of measured and calculated NOx concentrations under different operating conditions

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Fig. 3

HRR and NO emissions (2000 rpm, SOI@–12ca, no EGR)

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Fig. 4

Linear relationship between predicted NO emissions and NOx formation intensities: (a) 3000 rpm and (b) 2000 rpm

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Fig. 5

Model-based EGR control algorithm

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Fig. 6

Model-based EGR valve control results: (a) load and rpm, (b) NOx prediction and EGR valve position, and (c) measured NOx

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